MXPA96004425A - Molding material made with aditi - Google Patents

Abstract

The present invention is related to a composition comprising polystyrene or polypropylene with at least 0.05% (w / w) of an additive or humectant people, the article of manufacture consisting of the same, such as a mold for making contact lenses and the mold assembly containing the mold and the use of such a mold to minimize defects such as holes, puddles, splinters and drops in the mold

Description

MOLDING MATERIAL MADE WITH ADDITIVES DESCRIPTION OF THE INVENTION The present invention relates to a new polymer formulation, containing an internal mold release additive which aids in the release of one mold component from another or a wetting agent of the internal mold, which increases the interfacial wetting between the Mixture of reactive monomer and mold surfaces, thereby reducing the amount of defects formed in the contact lens. The present invention is also related to the molds made from such a polymeric formulation, as well as to a method for preparing contact lenses from these molds. An extensive arrangement of methods is currently used in the manufacture of hydrophilic polymer articles, such as soft contact lenses. A considerable variety of techniques have been employed, such as rotary casting, static casting molding, contouring and a combination of casting and turning and particularly through the use of two-part molds. Generally, such mold parts for hydrophilic contact lenses consist of a curvilinear center (concave / convex) of the curved, front mold part adapted to form, in cooperation with a curved part of the coupling base mold, a mold of two. parts for contact lenses. These hydrophilic contact lenses usually consist of a hydrophilic polymer, preferably a polymer based on HEMA (hydroxyethyl methacrylate), among numerous other materials. The mold components within which the hydrophilic polymer contact lenses are molded can consist of suitable platforms, each including a plurality of cavities that receive parts of the mold having female and / or male base surfaces or portions of the mold. Curvilinear mold for the formation of curved contact lenses. The molds, as described for example in the molding technology, can be constituted of conventionally selected conventional plastic materials, whereby the hydrophilic polymer articles, i.e. the contact lenses will be formed in the cavity between them and possibly Adhere to one or both parts of the mold. In the use of two-part molds, separable for the molding of hydrophilic contact lenses, upon completion of the molding step, it is of critical importance to be able to release the hydrophilic contact lenses from their surface coupling without adhesion to the parts. of the mold or at least one of the mold halves to separate the mold part without causing damage to the contact lens, which would render the lenses unusable. Unfortunately, too often, the damage is sustained during the preparation of contact lenses. Potential damages which generally render contact lenses unusable to meet the necessary standards of quality and / or inspection, may consist of edge drops and chips, slots or other surface defects formed in contact lenses. Other causes of the rejected are holes, spaces in the center of the emptying that develop in the lenses during the molding process, small holes, ie areas without uniform thickness and puddles. As a result, there is a need to find a new formulation for the mold that would reduce the risk of damage and defects. The defects of the lens are major factors that cause low production yield. There are two different types of problems associated with the production of contact lenses, which the present invention is solving. One such problem is the appearance of splinters and drops in the lens. These are caused during the demolding step and are caused by the addition of the mold to the lenses. The present invention overcomes this problem by using an alternative material for one of the mold parts. This new material contains an additive that is added to the mold, which greatly reduces the adhesion forces between the lenses and the mold part, thereby facilitating the release of material from the mold and minimizing the risk of developing defects in the lens caused by and during the demolding step. . The second problem which is contemplated by the present invention, is the prevention of the formation of pits and puddles, which are developed in the lenses during the molding process. Holes are usually found as spaces in the center of the lens, while puddles are usually randomly or in three-branch shapes, and are usually found along the edge of the lens and are usually associated with the curved front mold or concave. According to the inventors, they are mainly caused by poor wetting of the surface of the mold surface by the reactive monomer mixture in the mounting of the mold surface. More specifically, poor wetting is usually due to either incompatible chemistry or incompatible charges through the interface of the mold and the reactive monomer mixture or the combination of both. More importantly, a heterogeneous mold surface, which causes uneven wetting by the reaction of the monomer mixture, results in many empty spaces without local wetting and therefore leads to holes or puddles in the contact lens. According to the inventors, these holes and puddles would be overcome if a wetting agent is first added to the polymer mold to increase the wettability of the mold. To understand the concept of wetting, a brief digression will be made to discuss the cases that occur at a molecular level in a liquid. In the body of a liquid, the force averaged over time exerted on any molecule given by its neighboring molecule is zero. Even though such a molecule can undergo diffusion displacements due to random collisions within the liquid, for any prolonged duration, there are no forces directed on it. There is an equal probability to be displaced in one direction like another. However, the situation is very different in the surface of the liquid, since there are no molecules to counteract the force exerted by the molecules in the interior for the molecules on the surface. As a result, molecules on the surface of a liquid experience a net attraction to the interior of a drop, causing the drop to assume a spherical shape, minimizing both the free energy and surface area. This creates a surface tension, which from a microscopic point of view is the reversible isothermal work, which must be done in the molecules that form the bridge from the interior of the liquid to the surface and create 1 unit of new surface. The present inventors believe that by exceeding the surface tension, the potential to form "pits" in the liquid, ie, they vary to the spreadable or wettable liquid on a solid, would be eliminated. In the wetting or non-wetting of solids by liquids, the criteria used are the contact angle between the solid and the liquid (measured through the liquid). The reference is made to Figure 6, which illustrates the relationship between the contact angle "a" and the interfacial tensions that exist on the surface of a liquid. As it is clearly shown, there are three interfaces which exist when a drop of liquid makes contact with a solid, and in this way there are three corresponding interfacial tensions, SL, SV and LV, in which it refers to the interfacial tension S, L and V refer to a solid, liquid and vapor, respectively. It is said that a liquid moistens a solid, if the contact angle "a" is placed between 0 and 90 °, and does not wet the solid, if the contact angle is placed between 90 ° and 180 °. In equilibrium, there is a balance of interfacial tensions in the common contact line, which intersects Figure 6 at point 0. For a liquid that moisturizes the solid, this equilibrium is expressed by the relation:? SV =? SL -? LV COS? The present inventors have modified this concept and used this modification to determine if a particular substance can be used to reduce the tendency to form holes and puddles in the manufacture of contact lenses. In addition, the present inventors have found a tendency and thus have found that particular compounds when mixed with the polymeric mold material, significantly reduces the amount of holes and puddles in contact lenses. His solution is based on his understanding of the thermodynamics of the situation. They calculated that, the theoretical calculation of humidification, which is the thermodynamic parameter called the extension coefficient, is defined as: s =? 3 - yt - y, i where S is the extension coefficient, _ is the surface energy of the mold material, ^ is the surface tension of the reactive monomer mixture ("RMM") and g ^ is the interfacial tension between the reaction monomer mixture and the material of the mold. A positive "S" indicates the extension (or wetting). Therefore, to extend or moisturize, -_ and s ^ should be made as small as possible or g should be made as large as possible. Practically, this means that the surface energy of the mold is increased or the surface tension of the reactive monomer mixture is reduced or both are effected to obtain the proper wetting between the reactive monomer mixture and the mold. With respect to the increase of the surface energy of the mold, this requires the consideration of not only increasing the total surface energy, but also increasing the high energy portion of the surface. This can be done by various techniques for example, by coating the surface of one of the mold halves with surfactant, or by passing over a surface of the mold with a wetting agent. Another method, which is one embodiment of the present invention, is the incorporation of wetting agents within the mold material. Obviously, not all wetting agents for the mold material will be effective. The present inventors have developed a methodology for determining which mixtures will be useful for the composition of the mold material, for the manufacture of contact lenses having a reduced number of pits or puddles. As a result, the present inventors have developed a new mold material which has the added advantage of reducing the tendency to form pits or puddles. Therefore, the present inventors have developed new formulations for the mold that improve production and reduce defects in contact lenses. In one embodiment, the formulation of the present invention reduces the tendencies to form splinters and drops. In another embodiment, the present formulation reduces the tendencies to form holes and puddles in contact lenses. Accordingly, the present invention provides a mold for manufacturing contact lenses, comprising a thermoplastic polymer of either polystyrene or polypropylene mixed with a mold release agent, internal (additive) or wetting agent. More specifically, the present invention relates to a mold material constituting a mold half for use in the production of contact lenses, the mold material comprises a thermoplastic polymer and an internal additive, which is impregnated within the material thermoplastic and which is present in amounts in the range of about 0.05% to about 5% by weight, the thermoplastic material is polystyrene or polypropylene and the additive is a polyethylene or polypropylene wax having a molecular weight in the range of about 5,000 to about 200,000, an amide wax of the formula R1C0NH2, wherein R-_ is a hydrocarbyl group and the amide wax has a molecular weight of about 200-2, 000, silica having a molecular weight in the range of about 2,000 to about 100,000, Montana wax, oxidized wax, fatty acid having a molecular weight of about 200 to about 2,000, a complex ester or a combination thereof. The present invention is further related to a mold material constituting a mold half for use in the production of contact lenses, the mold material comprises polystyrene and an effective wetting amount of a wetting agent in admixture with it, the strength Moisturizer of the mold material is described by the equation: F = 2? J pcos? where F is the wetting force of the half of the mold _ is the surface tension of the distilled water p is the perimeter of the mold material in the meniscus, when the half of the mold is partially submerged in the water and is the dynamic contact angle, wherein the contact angle of the mold material is less than 100 °. When these materials are used to fabricate one of the mold halves in the assembly of the mold to manufacture the contact lenses, it was found that fewer lenses having the defects described in the foregoing were found. In this way, the present invention is also related to the half of the mold comprising this new formulation. This half of the mold is part of the assembly of the mold and therefore the present invention is still related to the assembly of the mold comprising the half of the mold consisting of these formulations of the present invention. More particularly, the present invention relates to a mold half useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly, comprising half of the mold and a second mold half, half of the mold comprises an integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at least the central portion of at least one of the concave surface and the convex surface, which have the dimensions of the back curve of the desired expanded or unexpanded contact lens, which is to be produced in the mold assembly and sufficiently uniform and contoured such that the surface of the contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable, the article has an annular projection, integral with the width and which e surrounds the circular circumferential edge and extending from there in a plane normal to the axis of the concave surface, the article also has a generally triangular tongue located in a plane normal with the axis y extending from the ledge, the article having effective thinness and rigidity to transmit heat through it and to withstand leverage forces applied to separate the mold half from the mold assembly and the article that is formed from the mold material consisting of a thermoplastic polymer mixed with an additive or agent anti-humectant as described in the above. The mold assembly preferably consists of at least two pieces, a female concave piece (front piece) and a male convex piece (back piece) that form a cavity between them and when the pieces are engaged, at least one piece has a ledge around it. More particularly, in a preferred embodiment, the mold assembly comprises a front mold half and a back mold half in contact therewith, whereby they define and enclose a cavity therebetween and a polymerizable composition in the cavity, in contact with the mold halves, the front mold of which has a central curved section with a concave surface, a convex surface and a circular circumferential edge, in which the portion of the concave surface in contact with the polymerizable composition, has the curvature of the front curve of a contact lens to be produced in the mold assembly and is sufficiently uniform such that the surface of a contact lens formed by polymerization of the polymerizable composition in contact with the surface, is optically acceptable, the The front mold also has an annular projection, integral with and surrounding the circular, circumferential edge and extending from it. n plane normal to the axis and extending from the projection, while the rear mold has a curved, central section with a concave surface, a convex surface and a circumferential edge, circular, in which the portion of the convex surface in contact with the polymerizable composition has the curvature of the posterior curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform such that the surface of a contact lens formed by polymerization of the polymerizable composition in contact with the surface is optically acceptable, the back curve also has an integral annular projection and surrounding circular circumferential edge and extending from there in a plane normal to the axis of the convex structure and a generally triangular tongue located in a plane normal to the axis extending from the projection, wherein the convex structure of the rear mold half makes contact with the circumferential edge of the front mold half. The inner concave surface of the middle of the front mold defines the outer surface of the contact lens, while the outer convex surface of the base mold half defines the inner surface of the contact lens, which rests on the edge. In this assembly, either the back mold of the front mold half or both is formed of the novel formulation of the present invention. However, it is the back mold half that is preferably formed of the novel formulation of the present invention, while the front bend mold is formed of a thermoplastic material, which does not contain the additive or wetting agent. In this way, the present invention is also related to the base mold consisting of the novel formulation. More specifically, the present invention relates to a mold assembly used in the production of a contact lens by the polymerization of a polymerizable composition in the mold assembly, the mold assembly comprises a front mold half and a mold half. in contact with it, so that they define and enclose a cavity between them, and a polymerizable composition in the cavity in contact with both of the mold halves, in which the front mold half comprises a first article of thermoplastic polymer, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circumferential, circular edge in which the portion of the concave surface in contact with the polymerizable compositions has the curvature of the front curve of a contact lens that is going to be produced in the mold assembly and is sufficiently uniform, in such a way to the surface of a contact lens formed by polymerization of the polymerizable composition in contact with the surface is optically acceptable; the first article has an annular projection, integral and surrounding the circular circumferential edge and extending from there in a plane normal to the axis of the convex surface, and generally the triangular tongue located in a plane normal to the axis and extending from the outgoing; the back mold consists of an integral article having a central curved section with a concave surface, a convex surface and a circumferential, circular edge in which the portion of the convex surface in contact with the polymerizable composition has the curvature of the posterior curve of a contact lens to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerization composition in contact with the surface is optically acceptable; the second article has an integral annular projection with and surrounding the circumferential edge, circular with and surrounding the circular circumferential edge and extending therefrom, in a plane normal to the axis of the convex surface and a generally triangular tongue located in a plane normal to the axis extending from the projection, wherein the convex surface of the rear mold half makes contact with the circumferential edge of the front mold half; the back mold is formed of a mold material consisting of a thermoplastic polymer mixed with an additive as described above. The mold assembly with the base curve mold made of the polystyrene / additive or polypropylene / additive formulations, polystyrene / wetting agent or polypropylene / wetting agent are used in the manufacture of soft contact lenses. In this way, the present invention is still related to the method of manufacturing soft contact lenses that use this mold assembly. That is, an improved method for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith so that it defines and encloses a cavity therebetween and that they contain the cavity a polymerizable composition in contact with the mold halves; the front mold half comprises a first thermoplastic polymer article, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of the concave surface in contact with the polymerizable composition, has the curvature of the front curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable; the back mold half comprises a second article of ultraviolet light transparent thermoplastic polymer, the article has a curved, central section with a concave surface, a convex surface and a circumferential circular edge, wherein the portion of the convex surface in contact with the polymerizable composition has the curvature of the posterior curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the composition polymerizable in contact with the surface is optically acceptable, wherein the convex surface of the back mold makes contact with the circumferential edge of the front mold half; and half of the front mold is held against the back mold half; and the polymerizable composition undergoes polymerization under precuration and curing conditions with ultraviolet light and the posterior curve is separated from the front curve and the contact lens during a demolding process and the front curve is subsequently separated from the contact lens, the improvement it comprises using a back bend mold that is formed from the mold material as described above.

As described herein, the use of the formulations of the present invention modifies the chemistry of the surface of the subsequent mold by increasing its wettability. further, a formulation of the present invention, facilitates the release of the polymerized polymer matrix comprising the contact lens and the front mold. Another aspect of the present invention is related to a method for minimizing and / or avoiding splinters or drops in the contact lens, using a mold consisting of polyethylene or polypropylene mixed with the additive described above, in amounts effective release of the mold. Another aspect of the present invention is related to a method for minimizing and / or avoiding holes or puddles in the contact lens, by the use of a mold half consisting of a thermoplastic material blended with an effective amount of a wetting agent, the thermoplastic material is polystyrene or polypropylene and the mold half is sufficiently wet to have a dynamic contact angle when immersed in water of 100 ° or less. The present invention can be more readily understood by one skilled in the art, with reference being made to the following detailed description of several of its preferred embodiments, taken in conjunction with the accompanying drawings, in which like elements are designated by reference numerals. identical in all the different views. Figure 1 is a flow diagram of the continuous process for the production of the contact lens, including molding, treatment and handling of molds and contact lenses in a low oxygen environment. Figure 2 is a plan view in upper elevation of the production line system constructed in accordance with the present invention. Figures 3 and 3 (a) are respectively a top view or a flat view and an elevation view of the side of an embodiment of a first curved mold (female) or molded front mold according to the present invention. Figure 3 (b) is an enlarged detail of a portion of Figure 3 (a). Figures 4 and 4 (a) are respectively a top or plan view and an elevation or side view of an embodiment of a second curved (male) or rear mold half, molded in accordance with the present invention. Figure 5 is a base curve configuration of 8 mold halves (cavities) supported and recorded on a platform consisting of several formulations, as described in Example 1. Figure 6 is a schematic diagram of the contact angle and the surface tension at the solid-vapor and solid-liquid interfaces of a solid immersed in a test liquid. Figure 7 is a schematic diagram of the methodology of the present invention used to measure the contact angle. Figure 8 is a diagram of the various parameters that determine the contact angle. Figure 9 is a typical drawing of water wetting force. As described in the above, the mold contains an internal additive or humectant agent. In other words, the additive or wetting agent is completely mixed with the thermoplastic polymer. This provides a substantially uniform distribution of these internal additives or wetting agents through the resin surface of the mold and decreases the likelihood that they will be retained in the lens. The polystyrene / additive, polypropylene / additive, polystyrene / wetting agent or polypropylene / wetting agent compositions are prepared by methods well known to those skilled in the art. The following procedures exemplify the technique used to prepare the formulations of the present invention, using polystyrene and an additive as an example. However, it is exemplary and is equally applicable for the preparations of the other formulations of the present invention. The polystyrene and the additive are mixed together by techniques known to one skilled in the art. In a methodology, polystyrene is composed of the additive. In other words, a predetermined amount of the additive and polystyrene are mixed together, the mixture is heated to melt the polystyrene, the molten polystyrene and the additive are then mixed together again, such as an extruder, which also intermixes the two components. The mixture can then be regranulated in a granulator. Alternatively, the polystyrene can not be melted first to form the molten polystyrene and the additive added to the molten polystyrene and the mixer, for example the extruder and mixed together and then regranulated with the granulator. Alternatively, the additive may be forming a composite with the thermoplastic material directly in the molding machine. The amount of additive added to the thermoplastic material is an effective amount that releases the mold, while the amount of added wetting agent is an effective wetting amount. The molded material consisting of it will be transparent to the transmission of UV light, especially from 3 to 5 nm up to 300 nanometer wavelengths. However, these preference quantities overlap. More specifically, when present, the additive or wetting agent is preferably present in an amount in the range of about 0.05% to about 5% (w / w) relative to the thermoplastic material and most preferably in the range of about 0.1% to approximately 2.5% (w / w). These mold formulations solve two different problems; in this way the mold formulation used is dependent on the objective. If the objective is to reduce the holes, the mold formulation used is the thermoplastic material mixed with the wetting agent. If the objective is to reduce puddles, the front curve mold is formed of the thermoplastic material with the wetting agent. On the other hand, if the objective is to facilitate the release of the lens mold, then the mold formulation used for at least one of the edges, preferably the back mold, is the thermoplastic material with additive. As used herein, reference to the "wetting formulation" or "composition" refers to the mold material formed of the thermoplastic material (e.g., polypropylene and most preferably polystyrene) and the wetting agent, as defined herein. . Alternatively, the reference to the "mold release formulation" or "composition" refers to the mold material formed of thermoplastic material (e.g. polypropylene or polystyrene) and the mold release agent. The reference to "formulations" or "compositions" of the present invention or the equivalent expression, which does not specify "mold release" or "wetness" refers to both formulations. The mold formulations of the present invention may consist of either the back curve mold, the front curve mold or both. Due to its healing surface differences, the wetting or adhesion strength at the RMM / posterior curve interface is different from that of the RMM / front curve interface. It is preferred that the back curve is formed from the material of the mold of the present invention. In the discussions that follow, reference will be made to the posterior curve, however unless stated otherwise, these discussions are equally applicable to the frontal curve and the use of the posterior curve is for illustrative purposes. To determine the suitability of a mold material for use in the back bend mold, to reduce the tendency to form holes in the contact lenses, the inventors developed a modified wetting method for measuring the wettability of the back bend mold. This method measures the wetting forces between the test wetting liquid (D.I. water) and the mold surface of the posterior curve defined by the ratio, F = 2 ?? pcos? wherein F is the wetting force (mg) of the mold half that is measured; - [_ is the surface tension of the test liquid, ie the water; p is the perimeter of the mold half in the meniscus (cm) when the half of the mold is partially submerged in the water; and it is the dynamic contact angle in degrees. A schematic diagram of the experimental preparation is given in Figure 7, although the various parameters are schematically represented in Figure 8. A sample (901) such as the posterior curve is suspended vertically in a microbalance (902). The test liquid (903), such as water, is slowly raised to submerge the posterior curve. The wetting force between the test liquid and the posterior curve as the probe fluid is being raised is measured by the microbalance which is recorded on a 905 recorder. A trace of the wetting forces as a function of the Distance displaced by the water meniscus (904) on the surface of the posterior curve is obtained. A trace of typical wetting force (back curve) of water is given in Figure 9. In this form, the value of p can be measured. The test liquid that is used to make these tests is a common liquid or solvent, which has a known surface tension. The preferred probe liquid is water, which has a surface tension of 72.75 dynes / cm at 20 ° C. From these measurements, the contact angle is calculated. The inventors have determined that a posterior curve with a dynamic contact angle with water less than or equal to 100 ° produces contact lenses with significantly fewer holes. It is more preferred that the contact angle is less than or equal to 90 °. It is still more preferred that the contact angle be less than or equal to about 75 °.

In this way, by mixing the appropriate wetting agent with the polystyrene or polypropylene forming the mold half thereof and measuring the contact angle according to the above procedure, it is an easy test to determine the suitability of using the mold half in the manufacturing process for contact lenses that have a decreased tendency for pits or puddles. The wetting agents used in the present invention are surface active chemical agents, such as lubricants, antistatic agents or surfactants, which when mixed with the mold material to form the posterior curve, effectively change the chemistry of the surface of the mold and its surface properties. The preferred wetting agents that are used are the wetting agents, normally used in the plastic arts which are not toxic to humans. They include nonionic surfactants, cationic surfactants and anionic surfactants. Especially preferred are salts of fatty acids containing 16-30 carbon atoms. Preferred salts are stearates. Stearates are salts of stearic acid. They include ammonium salts and their metal salts. The "metal stearates" as used herein, are metal salts of stearic acid. These metals include alkali metals, alkaline earth metals, ammonium salts, Group 13 metals, Group 14 metals and transition metals, such as Group 12. Examples of metals include zinc, sodium, calcium, lead, barium, cadmium, aluminum, lithium and the like. Examples include HYTECH RSN 248D, PETRAC CP-11LS, PETRAC CP-115G, PETRAC 22, SYN PRO CALCIUM STEARATE PG, SYN PROTYPE 114-36, ITCO F, WITCO EXTRA DENSE G, WITCO FP, COMETALS SODIUM STEARATE, SYNPRO SODIUM STEARATE ST, WITCO HEAT STABLE, INTERSTAB ZN-18-1, PETRAC ZN-4, MATHE CALCIUM STEARATE, MILJAC CALCIUM STEARATE, WITCO CALCIUM STEARATE, MATHE SODIUM STEARATE, WITCO SODIUM STEARATE, WITCO Tl, COAD 20, 21, 23, 26 USP , 27B, 27D, 27F, HYTECH RSN 1S31, MATHE ZINC STEARATE S, MATHE ZINC STEARATE 25S, MILJAC ZINC STEARATE, WITCO ZINC STEARATE, PLASTOLUBE, SYNPRO ACF, SYNPRO 8 (Synthetic Product of Zinc Stearate 8), WITCO 42, WITCO 11 and the like. Other preferred wetting agents are oxygen-containing amines such as ethoxylated tertiary amines, hydroxyalkylated tertiary amines (ie tertiary amines trisubstituted with alkyl groups containing 1-20 carbon atoms, of which at least one of the alkyl groups is substituted by hydroxy) and quaternary ammonium compounds, especially quaternary ammonium sulfate. Examples of oxygen containing amines are described in Kirk-Othmer "Encyclopedia of Chemical Technology", Vol. 22, p. 379-381, (1983), the contents of which are incorporated for reference. Preferred hydroxyalkyl tertiary amines are of the formula where R ^ and R12 are alkyl of 1-20 carbon atoms containing a hydroxy group and R ^ g is an alkyl group of 1-20 carbon atoms. Examples of quaternary ammonium salts are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 22, p. 383-384 (1983). Examples include ARMOSTAT 410R, manufactured by AKZO, (ethoxylated tertiary amine), ATMER 163R, manufactured by ICI Americas (N, N-BIS- (2-hydroxyethyl) alkylamine), CYASTAT LS, manufactured by CYTEC (3-lauramidopropyl) trimethylammonium methylsulfate, LAROSTATE 264A, manufactured by PPG (Soya Ethyl Dimethylethylammonium) and the like. Other examples of preferred wetting agents are listed in the following: Surfactant Supplier Antistat A21750 Polyccm Huntsman Ar ostat 310 Akzo, Ampacat Armostat 41 0 Akzo Armostat 375 Akzo Atmer 16 ICI Americas Chemstat 122 Chemax Chemstat 122 / 60DC Chemax Chemstat 182 Chemax Eurestat T22 Schering Berlin Kemamine AS650 Humko Antistatic KN 3-V Chemical Atmer 1002 ICI Americas InL Cyastat 609 Am. Cynamid Cyastat LS Am. Cynamid Cyastat SN Am. Cynamid Cyastat SP Am. Cynamid Eurestat 66 Schering Bedin Larostat 96 PPG Larostat 451, 477 PPG Markstat AL- 12 Argus Markstat AL-26, AL-48 Argus Neutro-Stat A (Conc.) Simco Addaroma IN Merix Aristac M & 2M CDC Infl. Antffog / Antstatic MCG Morix Antistat AS, 50059 Ferro Antistat AS50098 Ferro Antistat HTA Hftech Antistabc Agent 575 Houghton Angstatic Coating 1412 Coating Systems Aritistatc Spray Price-Driscoll Atmer 1 90 ICI Americas Atmer 8505 ICI Americas Atmos 150, Atmul 124 Humko Atmul 84 Humko The additives used in the present invention are materials that are known or commercially available. Release agents are also known. Preferred additives are silicones, amide waxes, fatty acids, polyethylene and propylene waxes, mineral wax, oxidized waxes and the like. As used herein, the term "Silicones" is a term applied to a range of materials based on a skeleton of oxygen and silicon polymer with a carbon containing a side chain of hydrocarbyl groups containing 1-6 carbon atoms. More specifically, it consists of a polymer having a structure consisting of alternating silicon and oxygen atoms of the formula: wherein each R may be different, but preferably the same and are a hydrocarbyl group and n is an integer in the range of 20 to about 1,500. The molecular weight of the silicone is in the range of 2,000 to 100,000 g / mol, inclusive. Silicones have very low surface tension, preferably 22-24 mN / mo din / cm In addition, the silicones contemplated for use by the present invention are physiologically inert, stable, heat resistant, chemically inert, colorless and odorless. The term silicones includes in other things, silicone oil and silicone wax, examples include ABILWAX 9800 and 9801, L-42, L-45, NM-1, VISC-10M, SF96, SF1080, SF18-850 DOW CORNING 200, 203, 230, KANTSTIK 406 NOO, KANTSTIK M-55, silicone wax (steroidimethicone), dimethylsilicone and the like As used herein, amide waxes are waxes having the formula R1CONH2 in which R- It is a hydrocarbyl radical and Rj ^ CON ^ has a molecular weight in the range of about 200 to about 2,000 g / mol.There may be complete saturation in R1 or there may be at least one carbon-carbon double bond in R1. of amide preferably have up to 40 carbon atoms, even It is preferred that the amide waxes contain 12-30 carbon atoms. The amide waxes also include higher fatty acid amides, ie, fatty acids with an even number of carbon atoms, in the range of 12-30 carbon atoms. Examples include CRODAMIDE ER, CRODAMIDE OR, CRODAMIDE SR, CRODAMIDE 203, CRODAMIDE 212, EURESLIP 58, KEMAMIDE E, PARICIN 285, PARICIN 220, PETRAC ERMIDE, PETRAC SLIP-EZE, PETRAC VIN-EZE, PETRAC SLIP-QUICK, ACRAWAX C (1,2-ethanediylbiscoctadecanamide), ADWAX 280, EBS WAX, HOSTALUB FA1, PARACIN 285, ROSSWAX 140, CRODAMIDE EBS, BUSPENSE 047, ER, OR, 203, 212 KEMAMIDE B, S, U, ethylene bis (stearamide ), oleamide, erucamide and the like. Examples of the fatty acid are CROD acid, stearic acid and the like. The polyethylene and propylene waxes as used herein, are low, medium or high density polyethylene or polypropylene waxes, respectively, having a molecular weight in the range of about 5,000 to 200,000 g / mol. Examples of polyethylene wax include EPOLENE C-13, C-14, C-15, C-17, C-18, E-10, N-10, N-ll, N-21, N-34, HOECHST WAX PE 190, STANWAX and the like. Examples of propylene waxes are EPOLEN N-15P and EPOLENE E-43P and the like.

Other waxes such as minerals were, for example Montana waxes can also be used. Montana wax contains three parts, the wax portion, the resin portion and the asphalt portion. The wax component of Montana wax is a long chain ester mixture of (C24-C30) (62-68% by weight), long-chain acids (22-26% by weight) and long-chain alcohols, ketones and hydrocarbons (7-15% by weight). The resin portion is about 70% by weight of terpenes and polyterpenes and 30% by weight of resin acid and oxirresinic acid, while the asphalt portion is believed to be polymerized esters of oxirresinic acid. Oxidized waxes are alkane hydrocarbons (paraffins) having a molecular weight of 100-2,000 g / mol.

They are crowned at the ends with either ester, carboxylic or hydroxy groups. Examples include carnauba wax and Rosswax, such as Rosswax 100 and 1343 and the like. As defined herein, the glycerol esters are glycerol hydrocarbyl esters having a molecular weight of 200 to 2,000 g / mol. They include monoglycerides, diglycerides and polyglycerides, including triglyceride fatty acids. Examples include PATIONIC 900, 901, 902, 907, 919, 1042, and 1042 K and the like. The alcohol esters contain 5-2,000 carbon atoms and include such species as LUBE 106 and the like.

The complex esters are copolymers of organic phosphate esters having a molecular weight of 200-2,000 g / mol which contain glycerides, organic acid derivatives and fatty acids. Examples include KANTSTIK FX-9 and Q and the like. The combination of the additives listed in the above or mixtures include MOLD EASE PCR, MOLD WIZ INT 33 PA, INT 38 H, INT 33 UDK and the like. It is preferred that the combination has a molecular weight in the range of 200 to 200,000 g / mol. As defined herein, the hydrocarbyl is an aliphatic, cycloaliphatic or aromatic moiety containing carbon and hydrogen atoms, having from 1 to 200 carbon atoms. The hydrocarbyl portion may be straight or branched chain or cyclic. If it is cyclical, the rings of preference are fused. The hydrocarbyl group can be completely saturated or partially saturated or fully aromatic or conjugated. The hydrocarbyl portion may contain at least one double bond. It is preferred that the hydrocarbyl group contains 1-100 carbon atoms. The most preferred additives are SF 1080 Silicone Oil, Int 38H Ester Complex, Kantstick Q Ester Complex, FC 430 Ester Complex, ABILR 9801 Wax, Silicone Wax (stearyldimethicone), SF 96-5 Silicone Oil, L-42, AcrawaxR C (1,2-ethanediylbis-octadecanamide), polystyrene 202, Ester FC 4331 Complex, Silicone Oil SF 18-350, L-45 (dimethylsilicone), wax ABILR 9801 (cetyldimethicone), VSC-10M, Carnauba Wax and Wax Ross 100. The most preferred additives are SF 1080 Silicone Oil, Int. 38H Ester Complex, Kantstick Q Ester Complex, FC 430 Ester Complex and Abilwax 9801 Silicone Oil. Exemplary formulations include polystyrene with the following additives or wetting agents in the indicated amounts.

ADDITIVE AMOUNT BY WEIGHT ABILWAX 9801 0.25% ABILWAX 9801 1.00% FC 430 0.25% KANTSTICK Q 0.25% KANTSTICK Q 1.50% SF 1080 0.5% SF 1080 0.25% AXEL 33 P / A 0.25% AXEL 33 P / A 2.50% AXEL 33-H 0.25% AXEL 38 -H 2.5% GE 1080 0.5% GE 1080 0.25% CYASTAT LS 0.05% CYASTAT LS 0.50% CYASTAT LS 1.00% ATMER 163 0.50% The composition of the present invention is used to replace articles of manufacture, of which polystyrene or polypropylene are normally used. In such an application, the composition of the present invention is employed to consist of a removable, two-part mold assembly used in the preparation of soft contact lenses. The mold is formed of at least two pieces, a concave piece, female and a convex piece, male forming a cavity between them, when such parts engage, with at least one projection around them. At least one of the pieces is formed from the composition of the present invention. In other words, both halves or one half of the mold is formed of the composition of the present invention. When only one half of the mold is formed of the composition of the present invention, the other half of the mold is formed of a thermoplastic polymer that is normally used to make mold halves for contact lenses, as described in the following. It is preferred that half of the base mold be formed of the composition of the present invention.

A preferred mold assembly is shown in Figures 3 and 3a, which illustrate respectively the top and side elevation views of a modality of a front mold half 10 useful in the production of a contact lens by the polymerization of a composition. polymerizable in a mold assembly consisting of two complementary front and base mold halves. As indicated, the mold halves are useful in the production of contact lenses in which the lenses can be made which are immediately ready for use and in which the unexpanded lenses can be made which need to be expanded (hydrated) to be Ready to use Although as indicated above, the half 10 of the front mold may be formed of the present formulation, it is preferred that the front mold half 10 be formed of a suitable thermoplastic polymer, which is sufficiently transparent to ultraviolet light, to allow it to irradiation through it with light to promote the subsequent polymerization of a soft contact lens. Examples of suitable materials include polyolefins such as polyethylene, low, medium and high density polypropylene, including their copolymers; poly-4-methylpentene; and polystyrene. Other suitable materials are polyacetal resins, polyacryl ethers, polyarylethersulfones, nylon 6, nylon 66 and nylon 11. Thermoplastic polyesters and various fluorinated materials such as fluorinated ethylene-propylene copolymers and ethylene-fluoroethylene copolymers can also be used. Other materials that can also be used for the front mold half are described in U.S. Patent No. 4,565,348. The most preferred material for the half of the front mold is polystyrene or polypropylene. The front mold half 10 defines a central curved section with an optical quality concave surface 15, which has a circumferential, circular dividing edge 14 extending around it. The dividing edge 14, shown in enlarged detail in Figure 3 (b), is advantageous to form a sharp and uniform plastic radius dividing line (edge) for subsequent molding of the soft contact lens. A generally parallel convex surface 16 is separated from the concave surface 15 and an essentially annular uniplanar projection 18 is formed by extending radially outwardly of the surfaces 15 and 16 in a normal plane (perpendicular) to the (rotational) axis of the concave surface 15. The concave surface 15 has the dimensions of the front curve (power curve) of a contact lens that is to be produced by the middle of the front mold and is sufficiently uniform such that the surface of a contact lens formed by the polymerization of a polymerizable composition in contact with the surface is of optically acceptable quality. The front mold half is designed with a thinness (typically 0.8 mm) and an effective stiffness to transmit heat through it quickly and to withstand leverage forces applied to separate the mold half from the mold assembly during the demoulding. Figures 4 and 4 (a) respectively illustrate upper, elevation and lateral tracks of one embodiment of a second, or rear curve mold half. The rear curve mold half is designed with all the same design considerations mentioned above with respect to the front curve mold half 10. The rear curve mold half 30 is preferably formed from the composition of the present invention. The rear curve mold half 30 defines a central curved section with a convex optical quality surface 33, a generally parallel concave surface 34 spaced apart from the convex surface 33 and an essentially annular uniplanar projection 36 formed extending radially outward from the surfaces 33 and 34 in a plane normal to the axis (of rotation) of the concave surface 34. The convex surface 33 has the dimensions of the posterior curve (which is placed on the cornea of the eye) of a contact lens that is to be produced by the base mold half and is sufficiently uniform in such a way that the surface of a Contact lens formed by the polymerization of a polymerizable composition in contact with the surface is of optically acceptable quality. The base mold half is designed with a thinness (typically 0.6 mm) to transmit heat through it quickly and the effective rigidity to withstand leverage forces applied to separate the mold half from the mold assembly during the demoulding. The mold halves 10, 30 generally define the triangular tabs 26, 37 integral with the projection which projects from one side of the projection. The tab 37 extends to the protruding injection tip, which supplies molten thermoplastic to the mold and also defines the band sections 22, 38, inclined (for example 45 °) to make the flow of the wave front uniform. polymer and thus avoid pressure jet, pressure jet marks, cavity markings, welding lines or other undesirable flows which could damage the optical quality of the mold half. The mold halves 10, 30 also define small circular projections 25, 35 which serve as traps in the molding process to immobilize small plugs of colder polymers that can be formed in the injection heat tip between the cycles.

The reactive monomer mixtures (polymerizable composition) which are polymerized in the mold assembly, consist of the two halves of the mold include copolymers based on 2-hydroxyethylmethacrylate ("HEMA") and one or more comonomers such as 2-hydroxyethyl acrylate. , methyl acrylate, methyl methacrylate, vinylpyrrolidone, N-vinyl acrylamide, hydroxypropyl methacrylate, isobutyl methacrylate, styrene, ethoxyethyl methacrylate, methoxytriethylene methacrylate / glycol, glycidyl methacrylate, diacetone acrylamide, vinyl acetate, acrylamide , hydroxytrimethylene acrylate, methoxyethyl methacrylate, acrylic acid, methacrylic acid, glycerol methacrylate and dimethylaminoethyl acrylate. Preferred polymerizable compositions are described in U.S. Patent No. 4,495,313 to Larsen, U.S. Patent No. 5,039,459 to Larsen et al., And U.S. Patent No. 4,680,336 to Larsen et al. ., which include anhydrous mixtures of a hydrophilic hydroxy ester, polymerizable acrylic acid or methacrylic acid and a polyhydric alcohol and a water-movable ester of boric acid and a polyhydroxy compound, preferably having at least 3 hydroxyl groups. Polymerization of such compositions, followed by displacement of the boric acid ester with water, produces a hydrophilic contact lens. The mold assembly of the present invention described herein can be used to fabricate hydrophobic or rigid contact lenses, but prefers the manufacture of hydrophilic lenses. The polymerizable compositions preferably contain a small amount of a crosslinking agent, usually 0.05 to 2% and more frequently 0.05 to 1.0%, of a diester or triester. Examples of representative crosslinking agents include: ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,2-butylene dimethacrylate, 1,3-butylene dimethacrylate, 1,4-butylene dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, dimethacrylate. of diethyl glycol, dipropylene glycol dimethacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, glycerin trimethylacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate and the like. Typical crosslinking agents usually, but not necessarily, have at least two ethylenically unsaturated double bonds. The polymerizable compositions generally also include a catalyst, usually from about 0.05 to 1% (w / w) of a free radical catalyst. Typical examples of such catalysts include lauroyl peroxide, benzoyl peroxide, isopropyl percarbonate, azobisisobutyronitrile and known redox systems such as the combination of ammonium persulfate-sodium metabisulfite and the like. Irradiation by visible light, ultraviolet light, electron beam or a radioactive source can also be employed to catalyze the polymerization reaction, optionally with the addition of a polymerization initiator. Representative initiators include camphorquinone, ethyl 4- (N, N-dimethylamino) benzoate and 4- (2-hydroxyethoxy) phenyl-2-hydroxyl-2-propyl ketone. The polymerization of the monomer or monomer mixture in the mold assembly is preferably carried out by exposing the composition to the polymerization under the initiation conditions. The preferred technique is to include initiators in the composition which work by exposure to ultraviolet radiation; and exposing the composition to ultraviolet radiation of an effective intensity and duration to initiate the polymerization and to allow it to proceed. For this reason, the mold halves are preferably transparent to ultraviolet radiation. After the precuration step, the monomer is again exposed to ultraviolet radiation in a healing step, in which the polymerization is allowed to proceed to term. The required duration of the remainder of the reaction can easily be assured experimentally by any polymerizable composition. As indicated in step 108 in Figure 1, the monomer or monomer mixture is degassed prior to filling the front curved mold half to remove the dissolved gases. The O2 is eliminated due to its harmful effect on the polymerization. Other gases, including N2 are removed to prevent the formation of gas bubbles, when the monomer is expelled from the pump line relatively high pressure, which supplies the filling nozzle, to find the pressure of atmospheric or subatmospheric N2 of the filling and assembly chambers. Contact lenses are prepared by various techniques known to the skilled artisan, except that at least one half of the mold is formed of a formulation of the present invention. For example, they can be prepared by the direct molding of hydrogel contact lenses, which is described in U.S. Patent Nos. 4,495,313 to Larsen, 4,565,348 to Larsen, 4,640,489 to Larsen et al., 4,680,336 to Larsen et al. ., 4,889,664 to Larsen et al., And 5,039,459 to Larsen et al. Another method is depicted schematically in Figures 1 and 2 as will be described in detail in the following. Also, see U.S. Patent No. 5,540,410 to Lust et al.

In the following description, the procedure is described in which the back curve mold is formed of the formulation of the present invention. This is exemplary only since the front curve mold or both of the rear curve mold and the front curve mold can be formed of the present formulation. For efficiency, ease of operation and cycle time, the front curve mold and the back bend mold are made using injection molding devices. It is preferred that the thermoplastic material for the front lens and the composition of the present invention for the back mold be provided in the form of granules or particles of relatively high surface area, which have been fully equilibrated with the oxygen available in the atmosphere . In this methodology, the mold is designed to produce parts of the lens mold formed completely directly, which is without the associated support structure such as a structure; consequently there is no need to dissociate the portion of the polymer material not necessary in the demolding and the parts of the lens mold can be directly collected by automated robotic means for delivery to the transport medium. In a given cycle, any number of mold parts can be prepared, but for handling convenience, typically 8 mold parts of the concave or convex configuration lens are prepared in a given cycle and are transferred by an automated robotic means to a platform aluminum or stainless steel in which they are received and supported in a spatial, regular arrangement adapted for other operations. It should be understood that in most stages of the continuous process, the inspection means are operational to effect the rejection of parts against the reference criteria; therefore, after injection molding, the generally visual inspection, using photoelectric means, for example, for such defects such as turbidity, defect of the mold as in the configuration due to the feeding of inadequate material and the like, can lead to rejection on the one hand and in this way on the waste. To maintain continuity and consistency in online operations, generally a complete mold cycle or platform of the lens mold parts will be ejected from the line after the discovery of a defect in either of a part of the lens mold. Each of the platforms contains a unique barcode number for use in platform tracking and quality control procedures using barcode scanners.

The apparatus for removing and transporting the mold lens parts of the mold to the transport means includes a manual means for receiving the mold parts and a supporting sub-assembly capable of the sliding and pivoting movement required for the transfer of the mold parts to the mold. means of transport that operates horizontally. As illustrated in Figures 1 and 2 the injection molds # 1 and # 2, shown in steps 101 and 102 in the flow chart of Figure 1, respectively mold the parts or sections of the front curved lens and rear curve respectively; they must be located in tandem as shown in Figure 2 or to shorten the exposure to the atmosphere they can even be located in a common plane that intersects a bifurcated transport line, even perpendicularly oriented to it in the same plane. The robotic means 103, 104 is provided adjacent to the mold register and the coupling station to receive the concave and convex lens molds, respectively and transferring the mold part to a low oxygen environment at a high production cycle rate , as noted in step 105. In the course of or after completing the degassing of the mold sections of the lens as indicated in 106 in Figure 1, the platforms containing the mold sections of the concave and convex lens are ordered in an interleaved relation and degas when they are enclosed in the feed conveyor, in such a way that the automated equipment can perform its operative intercoupling in the molding ratio . The sequencing conveyor 32 including the interleaving station 40 is closed and pressurized throughout its length with an inert gas, conveniently nitrogen. The amount of nitrogen is not critical, it being appropriate to use nitrogen pressure alone enough to effectively exclude the atmosphere under the operating conditions experienced. In the nitrogen tunnel surrounding the sequencing conveyor 32, the freshly prepared lens mold preforms are degassed as indicated in step 106 in Figure 1. The molds of the concave lens are filled with the monomer composition reagent in step 107 and the convex and concave lens molds are placed in register and pushed in a complementary molding relationship. The filling and mounting zone 50 surrounds a portion of the shipping or transport means, which supplies the mold sections of the concave and convex lens respectively to the platform area, and at the end of the zone transports the paired mold platforms. and filled to the precuration zone. The filling and assembly area illustrated in Figure 2 is defined by a geometrically appropriate, transparent enclosure, generally rectangular in cross section, formed of any suitable thermoplastic or metal and thermoplastic construction. As illustrated at 107 in Figure 1, the mold sections of the concave lens are filled with degassed monomer composition from step 108 and then transported to a mounting module that optionally has a vacuum chamber formed intermittently with the tunnel of nitrogen in which the molds of the filled concave lens are coupled with the convex mold sections in vertical alignment and in coupling relationship, such that the reactive monomer composition is trapped between the optical surfaces of the respective mold sections and at least partially sealed by the coupling of the dividing edge formed peripherally in each of the sections of the lens mold. If present, the vacuum is released. Then, the coupled mold is passed through nitrogen to the precuring station, as an integral part of the nitrogen tunnel. After assembly of the mold parts, the monomer of the incipient lens is precured in step 109 in the precuring module 60 of the present invention. The precuring procedure involves holding the mold halves in register and then preserving the monomer or monomer mixture to a gel-like state.

After precuration, the polymerization of the monomer or monomer mixture is completed in the healing tunnel 75 as indicated in step 110, with irradiation. In the curing zone (75), the monomer / diluent mixture is then cured in a UV oven so that the polymerization is completed in the monomer or monomers. This irradiation with visible actinic radiation or ultraviolet radiation produces a polymer / solvent mixture in the form of the final, desired hydrogel. In addition, the healing zone also has a heat source, which is effective to increase the temperature of the polymerizable composition at a temperature sufficient to assist in the propagation of the polymerization and to counteract the tendency of the polymerizable composition to contract during the period in which it is exposed to ultraviolet radiation. After the polymerization process is completed, the two halves of the mold are separated during a demolding step, leaving the contact lens in the first or half of the front curve mold, from which it is subsequently removed. It should be mentioned that the front and back curved mold halves are used for individual molding and then discarded or disposed of. Heating the mold of the posterior curved lens creates the differential expansion of the mold polymer by heating relative to the cooler lens polymer, which displaces one surface with respect to the other. The resultant shear force breaks the polymer mold / polymer lens adhesion and aids in separation of the mold portions. The higher the temperature gradient between the surfaces of the mold portions, the greater the shear force and the easier to separate the mold portions. This effect is greater when there is a maximum thermal gradient. As time goes on, heat is lost by conduction from the back mold portion within the lens polymer and the front mold portion and then collectively within the surrounding environment. The heated mold portion therefore is quickly removed in such a way that very little energy is transferred to the polymer lens, avoiding the possibility of thermal decomposition of the lens. The heating can be performed by techniques known to one skilled in the art, such as by steam, laser and the like. Laser demolding processes are described in U.S. Patent No. 5,294,379 to Ross et al. If the heating step is with hot air or steam, after the heating step, the rear curve is leveraged from the front curve and the mold in the mold assembly, as indicated in Step 111. Yes, on the other hand , the heating is by laser or infrared, leverage is not used and the posterior curve spontaneously separates from the frontal curve. The mold release assemblies 90 of the mold separation apparatus 90 physically lever the half of the rear curve mold of the front curve half 10 of each mold of the contact lens, to physically expose each contact lens located in the mold of the lens for transport to a hydration station for the hydration of the lenses. The leveraging procedure occurs under carefully controlled conditions, such that the half 30 of the posterior curve will be separated from the half 10 of the frontal curve without destroying the integrity of the lens formed in the lens mold. After the mold assemblies have been separated in the demolding apparatus 90, each platform containing the front curve mold halves with a polymerized contact lens exposed therein, is subsequently transported to a hydration station for hydration and demoulding. of the front curve lens mold, inspection and packaging, as indicated in Step 112. In the procedures described in the above, when the base mold does not contain the additive or humectant agent in it, many lenses that were formed were unusable because they had defects, such as splinters or edges with drops or holes, ie spaces in the center of the emptied lenses. Without wishing to join the theory, these defects are caused by two different mechanisms. The chips are caused during the demolding process and are noticed when the base curve is separated from the frontal curve using the lever mechanisms described in the foregoing. However, when the appropriate additive is present in the posterior curve, demolding is facilitated and the posterior curve is more easily removed. As a result, there is a highly reduced case of damaging the lens during the demolding step, in which the posterior curve is separated from the front curve and the lens, which remains in the frontal curve. Without wishing to join the theory, it is believed that the additive in the posterior curve modifies the adhesion forces between the lens and the base curve. For example, when only polystyrene is used, it adheres very strongly to the polymer material of the lens; however, when additive is added to the polystyrene, the presence of the additive weakens the frictional forces between the polystyrene and the lens material, making it easier to separate from the back curve of the lens and the mold of the front curve. In this way, there is less stress on the surface of the lens during the demolding, making it easier to separate.

In this way, in a leveraged action between the lens mold halves, as occurs during demolding, the lens will slide more easily from the half of the convex mold. Accordingly, when the posterior curve is made of the release formulation of the mold of the present invention, separating the posterior curve from the frontal curve and has become easy. Therefore, less severe conditions are required to demold those used up to now. In fact, in certain modalities such as with ABIL WAX 9801, demoulding occurs without the temperature gradient, thus eliminating the need for heat in the demolding stage. Thus, by using the compositions of the present invention to separate the back curve from the mold assembly, the lenses can be demolded in good correct yields after the low temperature demoulding tunnel, such as from about 60 to 70 ° C. The additives that are added to the mold material that effects these changes are the mold release agents, the oils, the soaps, the waxes and the like, described herein. Wetting agents, when added to the lens mold, increase the wetting of the mold material. These wetting agents include antistatic compounds ie alkoxylated amines and the quaternary ammonium complexes and stearic salts, described herein.

Without wishing to be bound by theory, the original polystyrene or polypropylene mold (ie, the mold without additional wetting agents) is believed to be a heterogeneous low energy surface having a small portion of high energy area. For example, the mold surface when formed of polystyrene has a free energy mold surface of 42 dynes / cm. A heterogeneous polystyrene or polypropylene mold surface with small portions of high energy surface area causes local non-wetting and spaces, which in turn leads to holes in the lens. The hole problem in the lens was a problem of the previous wetting between the reactive monomer mixture and the surface of the mold. When the wetting agent is added to the surface of the mold, it significantly improves its wetting capacity. The surface becomes more homogeneous and the high energy surface area is significantly increased. As a result, using the wetting formulation of the mold material of the present invention, instead of the typical formulation, the holes in the lens are significantly reduced. For example, using zinc stearate as the additive in a polystyrene back bend mold, the holes in the lens are reduced from the typical 10 to 15% to less than 2%.

However, in many cases even when the thermoplastic material is mixed with either a wetting agent or additive, the resulting contact lens does not have only a minimum of holes or droplets, respectively, but concomitantly therewith, contact lenses have performance. improved. For example, when contact lenses are prepared using a back curve formed of polystyrene and 1% zinc stearate as the wetting agent, as described above, the resulting contact lenses have significantly fewer holes. The puddles in the lens are also significantly reduced. Concomitantly with this, however, the amount of chips and droplets was decreased, with the lens performance improving from 7 to 9%. Although such a result may indicate that zinc stearate can also act as a mold release agent, other experiments show that zinc stearate does not act in that capacity. In a study measuring the demolding forces at various temperatures between the contact lens and the polystyrene mold, the results show that there was little or no effect when zinc stearate was used. The main effect on the release of the lens (or release of the lens) is due to the higher temperature. The observations of the operation of demolding the lens during production, show no difference in demolding between the molds with and without zinc stearate adhesion. Similarly, the posterior curve formed of Abilwax was not wettable according to the wetting test as described above. Produced, as expected based on the teachings of the present, contact lenses had significantly less splinters and drops. However, as shown in Example 8 under the conditions hereof, concomitantly, contact lenses were produced that have fewer pits. Unless otherwise indicated, the molecular weights are in units of grams per mole. In addition, unless stated otherwise, the percentages are given in percentages by weight. The present invention will be described more specifically by the following illustrative examples. However, it should be understood that these examples are described solely to illustrate the invention, but not to limit the scope of the present invention.

EXAMPLE 1 The molds were molded in Nestal of 60 tons from the candidate formulations listed in the following in Table 2, according to the procedure described herein. As described herein and shown in Figure 5, the platform contains 8 base mold halves (cavities) arranged as depicted herein. The mold halves consisted of the various formulations described in the following and the contact lenses were prepared according to the procedure described herein. The parameters of the mold are presented in the following Table.

TABLE 1 MOLD ANALYSIS C l O 3 Cß C I HUNTSMAN 202 (Polystyrene) MOLD # 1 RADIO 8 447 8,447 8,461 i 44 i P V 0.857 4,576 4,368 1,898 MOLD # 2 RADIO 8.448 8 457 8.4-t 8.4-19 P? / 0.891 3.742 4.51 1 0.986 MOLD # 3 RADIO 8.4-19 8,461 8,448 8 402 P / V 0.938 4.250 2.581 1.843 HUNTSMAN 202 / PVDF (Polystyrene) MOLD # 1 RADIO 8 872 8,881 8,879 8,875 P? 0.651 0.557 0.595 OR 633 MOLD # 2 RADIO 8 879 8 888 8887 1 877 P? 0.821 0.631 0.549 0 332 MOLD # 3 RADIO 8.839 to iiß 8.879 8.872 P? / 0.545 2.796 1 .323 2.297 HUNTSMAN 202 / 0.2225% SF1080 (Silicone oil) MOLD # 1 RADIUM 7.853 7.861 7 871 7.831 P? 0.361 0.677 0.396 0.839 MOLD # 2 RADIO 7,837 7,862 7 669 7,854 P? 0.856 0.430 0.578 0.695 MOLD # 3 RADIO 7 853 7,861 7,870 7,858 P? 0.579 0.724 0.214 0.900 FINAL ANALYSIS C l C-3 C 6 c-l HUNTSMAN 202 / 0.5% SF1080 (Silicone oil) MOLD # 1 RADIO 7 8S8 7.IS7 7.165 7 833 P? 0.326 0.551 0.412 0.5Í0 MOLD # 2 RADIO 856 7 839 7,167 7,134 P? 0 611 0.421 0.333 0.449 MOLD # 3 RADIO 7.IS6 7.851 7.167 7 854 P? / 0 339 0 331 0.388 0.534 LEGEND: C-1 cavity UNO of platform C-3 cavity TRES of platform C-6 cavity SIX of platform C-8 cavity EIGHT of platform P? / Roughness peak to valley, an intermediate measurement metric PVDF Composite floruro of polyvinyl In Table 1, P / V is a crude measure, in which the smaller number is a better result. Legend C refers to the cavity in a mold, in such a way that the data as presented eliminates the variations of the cavity. As can easily be seen from the data in Table 1, in all cases, when the additive, such as SF 1080 is present in the mold, the P / V valve was significantly lower than in its absence. In this way, the data clearly shows that molds using a mold containing the additive produced more uniform lenses.

EXAMPLE 2 Molds fabricated from the candidate sample formulations plus a control, indicated in the key to Table 2, were prepared in an Acuvue Pilot lens to manufacture lenses according to the procedure described in the present specification. The results are presented in Table 2 TABLE 2 TABLE 2 (CONTINUED) As can be easily seen by the data in the Table 2, the total amount of edge defects (chips and drops) is lower in all cases and significantly lower in many cases when additives are present.

EXAMPLE 3 In this series of experiments, a study was carried out to evaluate the demolding of different compounds plus a standard polystyrene based on base curves. The lenses (Formulation 14.0 Acuvue) were processed in a line in K Maximize laboratory according to the procedure described herein, using the vacuum reservoir and 30 seconds, UV pre-curing under weight. They had an additional four minutes of healing UV without weight at 60 ° in the simulated tunnel. The molds are kept thermoset in an oven with hot air circulation ± 1.5 ° C before demolding, transferred to an aluminum platform maintained at the same temperature and demolded immediately after the WK laboratory mark release 1, which simulates the movement of the brand 1 demodulator in the present, installed in the pilot line Maximize in Vistakon.

No steam was applied. Movement: 3.5 degrees 0.5 seconds fast 6.0 degrees 3.0 seconds slow 15 degrees 4.4 seconds slow (ends fast) One side is levered separately. The molds are inspected in a 10 × stereomicroscope immediately after demolding. The BC protrusions are broken, the lens is raised, the lenses are lost and the drops are recorded. The results of this demoulding inspection are shown in Table 3. All lenses, except those with broken projections, were hydrated in the simulated Maximize procedure: 5 minutes at 70 ° C, 0.05% Tween 80 in DI water, followed for 3 minutes in DI water + storage overnight in buffered saline. The lenses were inspected for visual defects in DL2 using the Vistakon pilot line standards. The conditions are indicated in Table 3.

TABLE 3 MATERIAL% CH + TR "% HO Polystyrene 20 3 Polystyrene / 0.5% GE 1080 20 3 Polystyrene / 1% - from ABILWAX 9801 8 2 Polystyrene / 4% from ABILWAX 9801 10 2"Average valve of 3 runs" "only one run was made Clave CH = Chips HO = Holes TR = Drops As clearly shown by the data, a preferred embodiment in this run is the polystyrene mold with ABILWAS, ie silicone wax which produced the contact lenses that have significantly less splinters and drops, than when the lenses were formed of polystyrene alone.

EXAMPLE 4 1% Zinc Stearate (Znst) is mixed with polystyrene to produce the back bend molds. Contact lenses are prepared in accordance with the procedures described herein. The number of holes and the total yield were measured and compared with a control, in which no additive was added. Three tests are carried out and the results are indicated in the following.

As it is clearly shown, the mold of the posterior curve formed of polystyrene mixed with stearate of Zinc showed significant hole reduction and significant increase in lens yields compared to those of the control.

EXAMPLE 5 Several surface active antistatic agents, indicated in the following, were mixed with the polystyrene to produce back curve molds. These contact lenses were prepared according to the procedure described herein and the number of holes measured and compared to the control in which no additive was used. The results are indicated in the following: EXAMPLE 6 Following the procedures of Examples 4 and 5, they used the following materials to make the posterior curves and the lenses were produced according to the description herein. The results are indicated in the following.

Lens Beads of Lenses Made Using Various Material of the Posterior Curve ^ The polystyrene base resin manufactured by Hunstman Chemicals Corp. The polystyrene base resin manufactured by Hunstmap Chemicals Corp. d The polystyrene base resin manufactured by Dow Chemicals. The polystyrene base resin manufactured by Dow Chemicals.

EXAMPLE 7 1% Zinc Stearate is mixed with polystyrene to produce the back bend molds. The contact lens was prepared according to the methods described herein, except that the cure temperatures were modified. The% of returns are indicated in the following.

As shown in the foregoing, lenses made using moles with 1% zinc stearate under a wide temperature range give approximately the same high yields. Also, they give fewer holes. In this way, zinc stearate modified the molds which allows a wide range of variations in the curing conditions and does not affect the performance of the lens.

EXAMPLE 8 Several soft contact lenses were prepared according to the above procedures, using a back mold half made of either polystyrene or polystyrene and additive as described above. After the mold halves were separated by leverage, the percentage of holes in the contact lens produced by that mold were determined. The results are tabulated in the following.

Type of Material% of Holes 1. Polystyrene 5.4 2. Polystyrene 3.8 3. Polystyrene 1.8 4. Polystyrene 3.2 5. Polystyrene + 1% 0.1 of Abil ax 9801 6. Polystyrene + 1% 0.5 of SF1080 7. Polystyrene + 3% 0.9 of Axel ax 33 RD 8. Polystyrene + 1% 1.2 of FC430 9. Polystyrene + 2.0% 0.4 of Axelwax 38H As is easily shown under these conditions, there were fewer holes in the contact lens, when the back mold had an internal additive. The above preferred embodiments and examples are given to illustrate the scope and spirit of the present invention. The modalities and examples described herein, will make apparent to those skilled in the art other modalities and examples. These other embodiments and examples are within the contemplation of the present invention. Therefore, the present invention should be limited only by the appended claims.

Claims (52)

NOVELTY OF THE INVENTION CLAIMS

1. A mold material constituting a mold half for use in the production of contact lenses the mold material is characterized in that it comprises a thermoplastic polymer and an internal additive, which is impregnated in the thermoplastic material and which is present in the mold. amounts in the range of about 0.05% to about 5% by weight, the thermoplastic material is polystyrene or polypropylene and the additive is a polyethylene or polypropylene wax having a molecular weight in the range of about 5,000 to about 200,000, a wax of amide of the formula R1CO H2 wherein R ^ is a hydrocarbyl group and the amide wax has a molecular weight of about 200-2000, silicone having a molecular weight in the range of about 2000 to about 100,000, Montana wax, wax oxidized, fatty acid having a molecular weight of about 200 to about 2000, a complex ester or a combination of yourselves

2. A mold material constituting a mold half for use in the production of contact lenses, the mold material is characterized in that it comprises polystyrene and an effective wetting amount of a wetting agent mixed therewith, the wetting force of the mold material is described by the equation: F = 2 ?! pcos? where F is the wetting force of the mold half. 1 is the surface tension of distilled water p is the perimeter of the mold material in the meniscus, when half of the mold is partially submerged in water and? is a dynamic contact angle, in which the contact angle of the mold material is less than 100 °.

3. The mold material according to claim 1, characterized in that the amide wax is a fatty acid amide wax.

4. The mold material according to claim 1, characterized in that the thermoplastic polymer is polystyrene.

5. The mold material according to claim 1, characterized in that the thermoplastic polymer is polypropylene.

The mold material according to claim 1, characterized in that the additive is present in amounts in the range from about 0.1 to about 2.5% by weight.

7. The mold material according to claim 1, characterized in that the additive is silicone.

8. The mold material according to claim 2, characterized in that the additive is an unsightly or lubricating agent.

9. The mold material according to claim 2, characterized in that the wetting agent is an ethoxylated amine, a tertiary hydroxyalkyl amine or quaternary ammonium sulfate, stearic acid or its salt.

The mold material according to claim 9, characterized in that the wetting agent is ethoxylated tertiary amine, N, -N-Bis (2-hydroxyethyl) -alkylamine, zinc stearate, (3-lauramidopropyl) trimethylammonium methylisulfate, or dimethylethylammonium soy etosulfate.

11. A mold half useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly, formed of the mold half and a second mold half, the mold half is characterized in that it comprises a mold half. integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at least the central portion of at least one of the concave surface and the convex surface have the dimensions of the posterior curve of the expanded or unexpanded contact lens desired to be produced in the mold assembly and which is sufficiently uniform and contoured, such that the surface of the contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable, the article has an annular projection integral with the width and surrounding the circular circumferential edge and which extends from there in a plane normal to the axis of the concave surface, the article also has a generally triangular tongue located in a plane normal to the axis and extending from the projection, the article has a thinness and effective rigidity to transmit heat through it and to support leverage forces applied to separate the half of the mold of the mold assembly and the article is formed of the mold material consisting of a thermoplastic polymer mixed with an additive or an anti-wetting agent according to claim 1.

12. The mold half according to claim 11, characterized because the additive is fatty acid amide.

13. The mold half according to claim 11, characterized in that the thermoplastic polymer is polystyrene.

14. The mold half according to claim 11, characterized in that the thermoplastic polymer is polypropylene.

15. The mold half according to claim 11, characterized in that the additive is present in amounts in the range of about 0.1 to about 2.5% by weight.

16. Half of the mold according to claim 11, characterized in that the additive is silicone.

17. A mold half useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly, formed of the mold half and a second mold half, the mold half is characterized in that it comprises a mold half. integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at least the central portion of at least one of the concave surface and the convex surface have the dimensions of the posterior curve of the desired expanded or unexpanded contact lens to be produced in the mold assembly and which is sufficiently uniform and contoured, such that the surface of the contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable, the article has an annular projection integral with the width and surrounding the circular circumferential edge and which e extends from there in a plane normal to the axis of the concave surface, the article also has a generally triangular tongue located in a plane normal to the axis and extending from the projection, the article has a thinness and effective rigidity to transmit heat through it and to support leverage forces applied to separate the mold half from the mold assembly and the mold half which is formed from a mold material formed of polystyrene mixed with a wetting agent according to claim 2.

18 The mold half according to claim 17, characterized in that the contact angle of the mold material is less than or equal to 90 °.

19. The mold half according to claim 17, characterized in that the wetting agent is an ethoxylated amine, a tertiary hydroxyalkyl amine or a quaternary ammonium sulfate, stearic acid or its salt.

The mold half according to claim 17, characterized in that the contact angle of the mold material is less than or equal to 75 °.

21. The mold half according to claim 17, characterized in that the amount of wetting agent present is from 0.05% to 5% (w / w).

22. The mold half according to claim 21, characterized in that the amount of wetting agent present is in the range of 0.1% to 2.5% (w / w).

The mold half according to claim 17, characterized in that the mold material is ethoxylated tertiary amine, N, N-Bis (2-hydroxyethyl) -alkylamine, zinc stearate, (3-lauramidopropyl) trimethylammonium methylisulfate, or dimethylethylammonium soy etosulfate.

24. A mold assembly used in the production of a contact lens, by the polymerization of a polymerizable composition in the mold assembly, the mold assembly is characterized in that it comprises a front mold half and a back mold half in contact with it, so they define and enclose a ca between them and a polymerizable composition in the ca in contact with both halves of the mold, characterized in that the front mold half comprises a first thermoplastic polymer article transparent to ultraviolet light, the article it has a central curved section with a concave surface, a convex surface and a circumferential, circular edge in which the portion of the concave surface in contact with the polymerizable composition has the curvature of the front curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, in such a way that the surface of a co ntact formed by the polymerization of the polymerizable composition, in contact with the surface is optically acceptable; the first article has an annular projection, integral with and surrounding the circular circumferential edge and extending thereon in a plane normal to the axis of the concave surface and generally a triangular tongue located in a plane normal to the axis and extending from the outgoing; the back mold formed of an integral article having a central curved section, with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of the convex surface in contact with the polymerizable composition has the curvature of the curve a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerization composition in contact with the surface is optically acceptable; the second article has an annular projection, integral with and surrounding the circular circumferential edge with and surrounding the circular circumferential edge and extending from there in a plane normal to the convex surface axis and a generally triangular tongue located in a plane normal to the axis extending from the projection, wherein the convex surface of the rear mold half makes contact with the circumferential edge of the front mold half; the back mold is formed of a mold material consisting of a thermoplastic polymer mixed with an additive according to claim 1.

25. The mold assembly according to claim 24, characterized in that the additive is an amide wax of fatty acid.

26. The mold assembly according to claim 24, characterized in that the thermoplastic polymer is polystyrene.

27. The mold assembly according to claim 24, characterized in that the thermoplastic polymer is polypropylene.

28. The mold assembly according to claim 24, characterized in that the additive or wetting agent is present in amounts in the range from about 0.1 to about 2.5% by weight.

29. The mold assembly according to claim 24, characterized in that the additive is silicone.

30. A mold assembly used in the production of a contact lens, by the polymerization of a polymerizable composition in the mold assembly, the mold assembly is characterized in that it comprises a front mold half and a back mold half in contact with it, so that they define and enclose a cavity between it and a polymerizable composition in the cavity in contact with both halves of the mold, in which the front mold half comprises a first thermoplastic polymer article transparent to ultraviolet light, the The article has a central curved section with a concave surface, a convex surface and a circumferential, circular edge at which the portion of the concave surface in contact with the polymerizable composition has the curvature of the front curv of a contact lens that will is produced in the mold assembly and is sufficiently uniform, in such a way that the surface of a contact lens formed by the limerization of the polymerizable composition, in contact with the surface is optically acceptable; the first article has an annular projection, integral with and surrounding the circular circumferential edge and extending from there in a plane normal to the axis of the concave surface generally a triangular tongue located in a plan normal to the axis and extending from the projection; the back mold formed of an integral article having a central curved section, with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of the convex surface in contact with the polymerizable composition has the curvature of the curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerization composition in contact with the surface is optically acceptable; the second article has an annular projection, integral with and surrounding the circular circumferential edge with and surrounding the circular circumferential edge and extending from there in a plane normal to the axis of the convex surface and a generally triangular tongue located in a plane normal to the axis extending from the projection, wherein the convex surface of the rear mold half makes contact with the circumferential edge of the front mold half; the back mold is formed of a mold material consisting of polystyrene mixed with a wetting agent according to claim 2.

31. The mold assembly according to claim 30, characterized in that the contact angle is less than 90 °. .

32. The mold assembly according to claim 30, characterized in that the wetting agent is an ethoxylated amine, a tertiary hydroxyalkyl amine, quaternary ammonium sulfate, stearic acid or its salt.

33. The mold assembly according to claim 30, characterized in that the wetting agent is ethoxylated tertiary amine, N, N-Bis (2-hydroxyethyl) -alkylamine, zinc stearate, (3-lauramidopropyl) trimethylammonium methylisulfate, or ethosulfate soy dimethylethylammonium.

34. The mold assembly according to claim 30, characterized in that the contact angle is less than or equal to 75 °.

35. The mold assembly according to claim 30, characterized in that the wetting agent is present in amounts in the range of about 0.05% to 5% (w / w).

36. The mold assembly according to claim 35, characterized in that the wetting agent is present in amounts in the range of about 0.1% to about 2.5% (w / w).

37. In an improved method for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith, thereby defining and enclosing a cavity therebetween, and containing in the cavity a polymerizable composition in contact with the mold halves; half of the front mold comprising a first thermoplastic polymer article, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circumferential, circular edge in which portion of the concave surface in contact with the polymerizable composition has the curvature of the front curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the composition polymerizable in contact with the surface is optically acceptable; the rear mold half comprising a second thermoplastic polymer article, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circumferential circular edge, wherein the portion of the convex surface in contact with the polymerizable composition has the curvature of the posterior curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable, wherein the convex surface of the back mold makes contact with the circumferential edge of the front mold half; and the front mold half is clamped against the back mold half; and the polymerizable composition undergoes the polymerization under precuration and curing conditions with ultraviolet light and the back curve is separated from the front curve and the contact lens during a demolding process and the front curve is subsequently separated from the contact lens, the improvement is characterized in that it comprises using a back curve mold which is formed of the mold material according to claim 1.

38. The method according to claim 37, characterized in that the thermoplastic polymer is polystyrene.

39. The method according to claim 37, characterized in that the thermoplastic polymer is polypropylene.

40. The method according to claim 37, characterized in that the additive is present in amounts in the range of 0.1 to 2.5% by weight.

41. The method according to claim 37, characterized in that the additive is silicone.

42. In an improved method for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith, thereby defining and enclosing a cavity therebetween, and containing in the cavity a polymerizable composition in contact with the mold halves; half of the front mold comprising a first thermoplastic polymer article, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circumferential, circular edge in which portion of the concave surface in contact with the polymerizable composition has the curvature of the front curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the composition polymerizable in contact with the surface is optically acceptable; the rear mold half comprising a second thermoplastic polymer article, transparent to ultraviolet light, the article has a central curved section with a concave surface, a convex surface and a circumferential circular edge, wherein the portion of the convex surface in contact with the polymerizable composition has the curvature of the posterior curve of a contact lens that is to be produced in the mold assembly and is sufficiently uniform, such that the surface of a contact lens formed by the polymerization of the polymerizable composition in contact with the surface is optically acceptable, wherein the convex surface of the back mold makes contact with the circumferential edge of the front mold half; and the front mold half is clamped against the back mold half; and the polymerizable composition undergoes the polymerization under precuration and curing conditions with ultraviolet light and the back curve is separated from the front curve and the contact lens during a demolding process and the front curve is subsequently separated from the contact lens, the improvement is characterized in that it comprises using a back curve mold which is formed of the mold material according to claim 2.

43. The method according to claim 42, characterized in that the contact angle is less than or equal to 90 °.

44. The method according to claim 42, characterized in that the contact angle is less than or equal to 75 °.

45. The process according to claim 42, characterized in that the wetting agent is present in amounts in the range of about 0.05% to about 5% (w / w).

46. The method according to claim 42, characterized in that the wetting agent is present in amounts in the range of about 0.1% to about 2.5% (w / w).

47. The process according to claim 42, characterized in that the anti-wetting agent is an ethoxylated amine, tertiary hydroxyalkyl amine or quaternary ammonium sulfate, stearic acid or its salt.

48. The process according to claim 42, characterized in that the mold material is ethoxylated tertiary amine, N, N-Bis (2-hydroxyethyl) -alkylamine, zinc stearate, (3-lauramidopropyl) trimethylammonium methylisulfate, or ethosulfate of soy dimethylethylammonium.

49. The mold material according to claim 2, characterized in that the wetting agent is present in amounts in the range of about 0.05% to 5% (w / w).

50. The mold material according to claim 49, characterized in that the wetting agent is present in amounts in the range of 0.1% to 2.5% (w / w).

51. The mold material according to claim 2, characterized in that the dynamic contact angle is less than or equal to about 90 °.

52. The mold material according to claim 51, characterized in that the dynamic contact angle is less than or equal to about 75 °.